Planar differential current pickup for wireless power transmission

Abstract

Apparatus and methods for sensing current carried by one or more planar conductors is described. A plurality of sensing coils may be fabricated adjacent to one or more planar, current-carrying conductors. The sensing coils may detect a magnetic field generated by time-varying current flowing through the one or more planar conductors. The sensing coils may be arranged to cancel uniform and linear-gradient magnetic fields.

What is claimed is: 
     
       1. A current sensor for a pair of conductors that carry an electrical current, the current sensor comprising:
 a first winding located on a first side of a first conductor of the pair of conductors; 
 a second winding located between the first conductor and a second conductor of the pair of conductors, wherein the second conductor is configured to carry the electrical current in a direction opposite to a flow of the electrical current in the first conductor; and 
 a third winding located on a first side of the second conductor, wherein an area of the second winding is approximately equal to a sum of an area of the first winding and an area of the third winding to generate negligible current from background time-varying magnetic fields. 
 
     
     
       2. The current sensor of  claim 1 , wherein the first winding and third winding are wound in a first winding direction that is opposite a second winding direction for the second winding. 
     
     
       3. The current sensor of  claim 1 , wherein the pair of conductors, first winding, second winding, and third winding are planar. 
     
     
       4. The current sensor of  claim 3 , wherein the pair of conductors are formed on a printed circuit board or an integrated circuit. 
     
     
       5. The current sensor of  claim 1 , wherein the first winding, second winding, and third winding are arranged to generate negligible total secondary current due to a spatially-uniform, time-varying magnetic field passing through the first winding, second winding, and third winding that is generated by a source other than the pair of conductors. 
     
     
       6. The current sensor of  claim 1 , further comprising a wireless power transmit coil connected to the pair of conductors. 
     
     
       7. The current sensor of  claim 1 , further comprising a current sensing circuit connected to at least the first winding. 
     
     
       8. A current sensor for a pair of conductors that carry an electrical current, the current sensor comprising:
 a first winding located on a first side of a first conductor of the pair of conductors; 
 a second winding located between the first conductor and a second conductor of the pair of conductors, wherein the second conductor is configured to carry the electrical current in a direction opposite to a flow of the electrical current in the first conductor; and 
 a third winding located on a first side of the second conductor, wherein the first winding, the second winding, and the third winding form a single, continuous conductive path. 
 
     
     
       9. The current sensor of  claim 8 , wherein a first portion of the single, continuous conductive path is formed on a first level and a second portion of the single, continuous conductive path is formed on a second level. 
     
     
       10. The current sensor of  claim 9 , wherein the pair of conductors are formed on a third level. 
     
     
       11. The current sensor of  claim 1 , further comprising:
 at least one additional first winding located on the first side of the first conductor; 
 at least one additional second winding located between the first conductor and the second conductor; and 
 at least one additional third winding located on the first side of the second conductor. 
 
     
     
       12. The current sensor of  claim 11 , wherein the first winding and the at least one additional first winding form a plurality of first windings, the second winding and the at least one additional second winding form a plurality of second windings, and the third winding and the at least one additional third winding form a plurality of third windings, and the plurality of first windings, the plurality of second windings, and the plurality of third windings form a single, continuous conductive path. 
     
     
       13. The current sensor of  claim 12 , wherein a first portion of the single, continuous conductive path is formed on a first level and a second portion of the single, continuous conductive path is formed on a second level. 
     
     
       14. The current sensor of  claim 12 , wherein the plurality of first windings, the plurality of second windings, and the plurality of third windings are formed from only two conductive levels of a printed circuit board or integrated circuit. 
     
     
       15. A current sensor comprising:
 a first planar winding having a first area and formed on a first side of a conductor; 
 a second planar winding having a second area approximately equal to the first area and formed on a second side of the conductor; and 
 a conductive via connecting a first portion of the first planar winding located on a first conductive level to a second portion of the first planar winding located on a second conductive level. 
 
     
     
       16. The current sensor of  claim 15 , wherein a first winding direction of the first planar winding is opposite a second winding direction of the second planar winding. 
     
     
       17. The current sensor of  claim 15 , wherein the conductor is located on a third conductive level of a printed circuit board or integrated circuit. 
     
     
       18. The current sensor of  claim 15 , wherein the first planar winding and the second planar winding are formed from a single, continuous conductive path.